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Post by brianbutler on Apr 3, 2021 15:20:41 GMT
A while back I bought three vintage Shimano skiptooth freewheels and refurbished the internals, where I didn't see any problems. I used one on a Viscount Aerospace GP and it works fine. I recently installed the other two on a Viscount Gran Sports and a Raleigh Super Course. All three bikes have Suntour V-GT Luxe (long cage) RD's, Suntour V-Comp FD's and Suntour ratchet shifters. All have new chains of the proper length. The chain skips on both recent bikes, one on the smallest cog and the other on the two smallest cogs. This happens on the large chainring, where I would usually be with those cogs. The chain line is OK and the chain is not contacting anything except the chain ring, cogs and derailleur pulleys. The B screw is set to provide as much wrap around the small cogs as possible. I have run out of adjustment options.
When I swap in a different freewheel with the same small cog size it works fine so at this point I think the teeth on the skipping cogs must be worn out but I can't tell by eye. They look small but not scooped out and the U between them is fairly symmetrical. Is there a measurement I can make to check?
If I get convinced that the cogs are worn out I will attempt to replace them but it will be a tough job. I have tried unsuccessfully to unscrew the small and next-to-small cog using two chain whips (one on the smaller cog and one on the next to largest cogs, turning counterclockwise. I broke (and repaired) a chain whip twice. Next I will have to make some type of jig out of an old crank or find a freewheel vise, then I'll have to find the right replacement cogs.
If anyone can suggest anything else I can try or check before embarking on this adventure, I would appreciate it.
Brian
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Post by franco on Apr 3, 2021 19:43:38 GMT
It sounds like you are right about wear on the teeth if the chain is slipping/jumping Brian but I’m afraid beyond that I don’t have any suggestions. I’m yet to delve into the world of rebuilding a freewheel.
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Post by triitout on Apr 3, 2021 21:55:41 GMT
I'm in agreement with Franco. No way I'm rebuilding a freewheel with my skills . In the old days, I'd just throw out the old freewheel and put a new one on with a new chain and problem solved. I'm rarely touching the smallest cog anymore so maybe you are just too strong! Maybe you can get away without shifting into the smallest cog. Two bad cogs doesn't seem rideable.
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Post by brianbutler on Apr 3, 2021 22:07:06 GMT
Rebuilding the freewheel internals is not too difficult and requires no special tools, actually just a hammer and nail set will do. A perfect job for a carpenter, eh Franco?
As far as not using the small cog, that's a good idea. I probably don't need it and could set the high limit to block shifts onto that cog. It would be nice to have that big 34T cog. It's really the principle of the thing. I'm irked that I can't see what is wrong with it. My only other data point on this topic is a freewheel I replaced on another bike that started skipping. It had many thousands of miles on it and looked worn. I replaced it with an identical freewheel and it cured the problem.
Brian
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Post by wheelson on Apr 3, 2021 23:44:56 GMT
Rebuilding the freewheel internals is not too difficult and requires no special tools, actually just a hammer and nail set will do. A perfect job for a carpenter, eh Franco? As far as not using the small cog, that's a good idea. I probably don't need it and could set the high limit to block shifts onto that cog. It would be nice to have that big 34T cog. It's really the principle of the thing. I'm irked that I can't see what is wrong with it. My only other data point on this topic is a freewheel I replaced on another bike that started skipping. It had many thousands of miles on it and looked worn. I replaced it with an identical freewheel and it cured the problem. Brian Sounds like wear that’s making it slip. The only other idea might be the chain. On some modern chains the outer link plates bulge and can cause slippage especially when cross chaining. Classic and modern chains may have a different amount of flexibility as well. I’d bet on tooth wear, though. At the shop, we measure the chain with a gauge. If it shows excessive chain wear we almost always replace the freewheel / cassette to prevent irate customers. I understand you got the freewheels unattached, and I know of no way to effectively measure wear on individual cogs. The freewheel body might be saved as some individual cogs can be found on eBay, like the “skip tooth” Shimano. At $20-25 a pop it might not be worthwhile, though. Best, John “wheelson”
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Post by brianbutler on Apr 4, 2021 12:27:02 GMT
Rebuilding the freewheel internals is not too difficult and requires no special tools, actually just a hammer and nail set will do. A perfect job for a carpenter, eh Franco? As far as not using the small cog, that's a good idea. I probably don't need it and could set the high limit to block shifts onto that cog. It would be nice to have that big 34T cog. It's really the principle of the thing. I'm irked that I can't see what is wrong with it. My only other data point on this topic is a freewheel I replaced on another bike that started skipping. It had many thousands of miles on it and looked worn. I replaced it with an identical freewheel and it cured the problem. Brian Sounds like wear that’s making it slip. The only other idea might be the chain. On some modern chains the outer link plates bulge and can cause slippage especially when cross chaining. Classic and modern chains may have a different amount of flexibility as well. I’d bet on tooth wear, though. At the shop, we measure the chain with a gauge. If it shows excessive chain wear we almost always replace the freewheel / cassette to prevent irate customers. I understand you got the freewheels unattached, and I know of no way to effectively measure wear on individual cogs. The freewheel body might be saved as some individual cogs can be found on eBay, like the “skip tooth” Shimano. At $20-25 a pop it might not be worthwhile, though. Best, John “wheelson” Thanks, John. I think it must be tooth wear, so these freewheels are going into the to-do box. Next winter when I'm looking for something to work on I will try to diagnose and repair them. That might involve creating a couple of tools: 1. A tool to measure tooth wear. How about pressing a new cog into clay or plaster and using it as a mold to make a tooth comparison tool? This could be overkill because it might be possible to measure tooth spacing directly but the curvature around the cog presents a problem. I'll try this right away to see if I can tell what is different between good and bad cogs.
2. A jig to spin off the tightly threaded small cog(s). I'm thinking an old frame and a crank with small chain ring could be used to turn the large freewheel cog clockwise while another fixed chain holds the small cog. I could slip a cheater bar over a crank arm for more leverage. The possible outcomes are a loosened cog, broken chain, bent frame, broken crank, or injury - stopping at the first occurrence.
If I can get the threaded cog off I can see if the cog from a modern, cheap Shimano freewheel has the same threading and dimensions. Might get lucky.
Brian
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Post by franco on Apr 4, 2021 12:48:47 GMT
Apparently, Rohloff make a tool for measuring cog wear Brian
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rodh
Viscount
Posts: 122
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Post by rodh on Apr 4, 2021 12:51:29 GMT
Do you happen to have a photo of the troublesome sprockets?
At first I wondered about chain stretch (what's the length for 23 complete links, 12"?). Then I wondered if the derailleur feeds vertically (i guess you checked the hanger alignment?), but now I'm thinking, is this a sprocket with flat top teeth (like UG), or twisted (like HG)?
I've had skating over the teeth with a modern chain on an old Maillard freewheel, but its quite different from the chatter you get with a new chain on an old sprocket, or the climb and jump you get with an old chain on a new freewheel.
Interesting problem ... keep us posted! Rod
PS ... nice name for that tool, Franco ... Roll-off was it?
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Post by wheelson on Apr 4, 2021 14:56:17 GMT
Do you happen to have a photo of the troublesome sprockets? At first I wondered about chain stretch (what's the length for 23 complete links, 12"?). Then I wondered if the derailleur feeds vertically (i guess you checked the hanger alignment?), but now I'm thinking, is this a sprocket with flat top teeth (like UG), or twisted (like HG)? I've had skating over the teeth with a modern chain on an old Maillard freewheel, but its quite different from the chatter you get with a new chain on an old sprocket, or the climb and jump you get with an old chain on a new freewheel. Interesting problem ... keep us posted! Rod PS ... nice name for that tool, Franco ... Roll-off was it? Good observations, both Brian and Rod. The skating on top of the tooth had slipped my memory. That was especially true of the old Maillard fw’s. I can’t remember if there were any “skip tooth” under the “Schwinn Approved” theme. Most of the skipped tooth were Shimano. Since you’re not using indexing, there shouldn’t be Shimano - Suntour conflicts. I’ll have to check out the video and research some more. Perhaps a length of new chain wrapped around the offending cogs (like a chain whip) and a go-no go connecting link or caliper to measure the connector difference? Oh oh, now you’ve got me started!!! Best (and Blessed Easter or what applies), John “wheelson”
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Post by brianbutler on Apr 4, 2021 19:53:51 GMT
Do you happen to have a photo of the troublesome sprockets? At first I wondered about chain stretch (what's the length for 23 complete links, 12"?). Then I wondered if the derailleur feeds vertically (i guess you checked the hanger alignment?), but now I'm thinking, is this a sprocket with flat top teeth (like UG), or twisted (like HG)? I've had skating over the teeth with a modern chain on an old Maillard freewheel, but its quite different from the chatter you get with a new chain on an old sprocket, or the climb and jump you get with an old chain on a new freewheel. Interesting problem ... keep us posted! Rod PS ... nice name for that tool, Franco ... Roll-off was it? Good questions Rod. It is a new chain. I have the RD adjusted so there is quite a bit of wrap around the small cogs. The hanger is straight and parallel to the dropouts. The teeth are flat topped. The skipping occurs under load on the two small cogs and seems to jump an entire link length, a couple of times per revolution of the FW but not consistent. Nothing seems to be interfering with the chain. Here is a close-up photo of the offending FW. Nothing looks obviously wrong to me so if the problem is with the cogs, it is subtle.
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Post by franco on Apr 4, 2021 22:22:39 GMT
Maybe try a different brand of chain Brian?
From what I know wear is usually on the left side of the teeth on the cogs not on the tops. In all fairness that FW looks inconsistently worn in places looking at the close picture, there are bright areas showing more wear than others. I’m guessing the previous owner ran a stretched chain on it for too long.
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rodh
Viscount
Posts: 122
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Post by rodh on Apr 4, 2021 23:25:21 GMT
Aha, square top teeth (a-la-Shimano UG) ... Try an old uniglide chain and that might fix it.
From the look of it I think it's not too worn at all but modern KMC z-chains definitely skate over what you have.
Best of luck, Rod
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Post by wheelson on Apr 5, 2021 0:02:05 GMT
Aha, square top teeth (a-la-Shimano UG) ... Try an old uniglide chain and that might fix it. From the look of it I think it's not too worn at all but modern KMC z-chains definitely skate over what you have. Best of luck, Rod Rod is right, that’s sort of the modern chain problem with the bulges and flexibility that I mentioned. If you can’t find a UG chain, KMC makes one marked 7 speed that is flat and approximates older chains and works better for friction shifting, not the ones marked 7 AND 8 speed which has bulged side plates. Best, John “wheelson”
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Post by brianbutler on Apr 5, 2021 2:09:25 GMT
OK, we're getting somewhere. I am using a KMC Z51 chain. I'll see if I can find a Shimano Uniglide. I also have a number of old cleaned chains that show less than 0.5% stretch that I could try for proof of concept. Thanks very much.
Brian
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Post by wheelson on Apr 5, 2021 2:23:28 GMT
OK, we're getting somewhere. I am using a KMC Z51 chain. I'll see if I can find a Shimano Uniglide. I also have a number of old cleaned chains that show less than 0.5% stretch that I could try for proof of concept. Thanks very much. Brian I think a Z6 or Z7 KMC might work if you can’t find a Shimano Uniglide. They have flat side plates but also use snaplink connectors. Best, John “w”
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Post by brianbutler on Apr 5, 2021 11:11:50 GMT
OK, we're getting somewhere. I am using a KMC Z51 chain. I'll see if I can find a Shimano Uniglide. I also have a number of old cleaned chains that show less than 0.5% stretch that I could try for proof of concept. Thanks very much. Brian I think a Z6 or Z7 KMC might work if you can’t find a Shimano Uniglide. They have flat side plates but also use snaplink connectors. Best, John “w” I ordered a Z6 last night so we'll see how that works. I am very interested to see the difference between the Z6, if it works, and the Z8.1 (formerly Z51). I really appreciate the advice I got here.
Brian
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Post by wheelson on Apr 5, 2021 12:25:49 GMT
I think a Z6 or Z7 KMC might work if you can’t find a Shimano Uniglide. They have flat side plates but also use snaplink connectors. Best, John “w” I ordered a Z6 last night so we'll see how that works. I am very interested to see the difference between the Z6, if it works, and the Z8.1 (formerly Z51). I really appreciate the advice I got here.
Brian
Please let us know how it works out. Most of the time we replace the chain and freewheel together at the shop and the freewheel has a modern tooth profile. The classic bikes I own haven’t been ridden enough due to my health issues to need a new chain. I do have a couple of Viscount rebuilds in the works so your feedback will be valuable. Best, John “wheelson”
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Post by brianbutler on Apr 5, 2021 20:14:04 GMT
I will definitely post what I learn. I am still somewhat amazed that the shape of the link sides can cause the skipping problem. I thought 5-6-7-8 speed chains were all 3/32" wide rollers, differing only in the overall outer chain width, which varies because of the plate thickness and pin length. So I usually order several chains at a time, all "8-speed" KMC Z8.1's, figuring the narrow outer width would fit through and derailleur cage. I should have been suspicious since they sell 6-speed and 7-speed specific chains. I have not had any problems with the Z8.1 on a variety of vintage Atom, Maillard, and Suntour freewheels, and all modern freewheels. The Shimano skip tooth freewheels are the first that manifested the problem, and not even on the unusual large skip tooth cogs.
John and/or Rod, specifically how does the skipping happen? Do the sides contact the freewheel? It did not look that way, but perhaps I don't understand what is happening.
Brian
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Post by wheelson on Apr 5, 2021 22:05:44 GMT
Brian, I sent you a gmail pm with a link, but here it is as well: www.google.com/url?q=https%3A%2F%2Fwww.bikeforums.net%2Fbicycle-mechanics%2F1078368-chains-work-well-old-5-speed-freewheels.html&sa=D&sntz=1&usg=AFQjCNEqDuNp9m6d5MNo_lP4HIC4xKMviAPay particular attention to the answer given by SBinNYC as he gives an excellent explanation of the situation based on chain designed specifically for indexing systems. I think you'll find that the Z6 and Z7 chains have the least amount of sideplate "alteration". Another thing he makes mention of is the upper pulley with intentional lateral movement. Shimano called this Centeron and had a wide and narrow version in their early indexing derailleurs. I too have used these in older non-indexing derailleurs and friction systems, with some degree of success. If you find used Centeron pulleys, make sure the play is only lateral as intended and not angular as the pulley bushing wears out. Best, John "wheelson"
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Post by brianbutler on Apr 6, 2021 0:29:40 GMT
Thanks, John. I believe SBinNYC is addressing poor performance when using a modern freewheel/chain combination with friction shifters. That's not my problem. I have a vintage freewheel and modern chain, with friction shifters of course. He describes shifting problems but my setup shifts very crisply but even when perfectly centered on the small cog, the chain slips under a load.
SBinNYC mentions the shape of the modern chain and how it interacts with a modern freewheel. I imagine it is the shape issue you are talking about.
If the Z6 chain does not solve the problem, I'll go back over everything again - chainline, chain tension, RD alignment, and top pulley position. The freewheel itself is nearly pristine so it is not a wear issue.
A good puzzle.
Brian
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Post by oldroadietehachapi on Apr 6, 2021 4:29:00 GMT
Yes, the old cog slip thing that seems to only strike when you least expect it. I usually replace old freewheels with a more modern Shimano TZ and use a KMC Z51 or 8 chain. This combo seems to shift oh so nice; I have even sacrilegiously paired the setup with Campy NR. Sometimes it is not possible; my PX10 has a Helicomatic freewheel and it sometimes skips on one cog. Perhaps it is the Z51 chain's curved side plates or perhaps the one cog is worn (looks OK). Helicomatic freewheels are getting few and far between with even used ones being hard to find. I have been looking for a chain that hopefully will fix the problem; You fine folks have inspired me to try a Z6 or Z7 chain.
All the Best Jim
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Post by brianbutler on Apr 6, 2021 11:06:57 GMT
Yes, the old cog slip thing that seems to only strike when you least expect it. I usually replace old freewheels with a more modern Shimano TZ and use a KMC Z51 or 8 chain. This combo seems to shift oh so nice; I have even sacrilegiously paired the setup with Campy NR. Sometimes it is not possible; my PX10 has a Helicomatic freewheel and it sometimes skips on one cog. Perhaps it is the Z51 chain's curved side plates or perhaps the one cog is worn (looks OK). Helicomatic freewheels are getting few and far between with even used ones being hard to find. I have been looking for a chain that hopefully will fix the problem; You fine folks have inspired me to try a Z6 or Z7 chain. All the Best Jim I'll let you know if the Z6 solves my problem, not that it would necessarily solve yours but it would be a sign of encouragement. I also use the modern Shimano TZ and KMC Z51 for replacements, but I have it in my head to use the Shimano skiptooth freewheels for the low gear and good looks. The low gear could be solved with the ugly Shimano megarange 6-speed freewheel but then I would have to put a bag over my wheel so I didn't have to look at it.
Brian
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Post by oldroadietehachapi on Apr 6, 2021 13:10:10 GMT
The Megarange is a homely thing. I may try one of these SRAM Freewheels. Looks to be a screw on that has cassette like cogs.
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Post by brianbutler on Apr 9, 2021 13:49:33 GMT
No joy with the KMC Z6 and Shimano 14-34 skiptooth FW. It still skips on the small cogs. Also, shifting is not as clean as with the KMC Z8.1 chain. I have now refitted the Viscount Gran Sports with a 14-28 Suntour Perfect 5, which runs silently and shifts flawlessly with the Suntour V-GT Luxe RD, Suntour V-Comp FD, and Suntour Power ratchet shifters. The only problem, of course, is the lack of a really low climbing gear. In theory I no longer need the long cage RD but it works perfectly and I might find a big-cog RD that works (Megarange, here we come) so I'll leave the long cage on there for now.
I contemplated taking the freewheel apart again to look for problems such as worn pawls but it seems to me that an internal problem occurring on the small cogs would be worse on the large cogs due to more leverage and higher stresses.
Final fun fact - the teeth on the Shimano are in perfect condition, as they are on the Suntour, but are 0.6mm wider (longer is maybe a better term) in the direction of rotation so they almost completely fill the gap between chain rollers, whereas the Suntour has some leeway. Both teeth are the same thickness.
Brian
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Post by wheelson on Apr 10, 2021 0:42:17 GMT
No joy with the KMC Z6 and Shimano 14-34 skiptooth FW. It still skips on the small cogs. Also, shifting is not as clean as with the KMC Z8.1 chain. I have now refitted the Viscount Gran Sports with a 14-28 Suntour Perfect 5, which runs silently and shifts flawlessly with the Suntour V-GT Luxe RD, Suntour V-Comp FD, and Suntour Power ratchet shifters. The only problem, of course, is the lack of a really low climbing gear. In theory I no longer need the long cage RD but it works perfectly and I might find a big-cog RD that works (Megarange, here we come) so I'll leave the long cage on there for now. I contemplated taking the freewheel apart again to look for problems such as worn pawls but it seems to me that an internal problem occurring on the small cogs would be worse on the large cogs due to more leverage and higher stresses. Final fun fact - the teeth on the Shimano are in perfect condition, as they are on the Suntour, but are 0.6mm wider (longer is maybe a better term) in the direction of rotation so they almost completely fill the gap between chain rollers, whereas the Suntour has some leeway. Both teeth are the same thickness. Brian Bummer, a real head-scratcher. I usually end up with the non-shifting triple front derailleur problem. For your problem I would have looked, in order, freewheel tooth wear, chain wear, chain wrap and “b” screw adjustment, derailleur pulley wear, dropout alignment, chain line, chain flexibility, . . . I guess Shimano and Suntour must hate each other! I have a Suntour Perfect gold 5 spd. with a 34 low, looks new but some varnish from sitting up. Yours for shipping if you want it. Best, John “wheelson”
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Post by brianbutler on Apr 10, 2021 2:29:20 GMT
That's about the order I tried things in and they checked out OK, including pulley wear, but I wonder if pulley wear makes any difference. I have a few old Huret RD's and the pulleys are made without teeth, just smooth discs. Of course those RD's shift like sh*t.
Sure, I'd like to have that Suntour Perfect 5. Text me the shipping cost and I'll pay you back. I actually have a Suntour Perfect 5 with 14-30 and another that is 14-32 but both are French threaded and I just put new wheels on the target bike (Weinmann LP18's on Origin8 sealed bubs, ISO threaded.) Ideally I'd also like to give you some parts. I know you have a lot of Lambert parts but is there anything you need for the diminutive Lambert project? I have a Lambert Pro with most of the original parts but it is a 62cm frame and I will never use it.
Regarding the non-shifting triple, I always wondered why half-step plus granny was a thing. I have a Fuji with a 50-46-30 triple. The explanation given is that the two big chainrings should be close in size so the FD isn't sitting way above the middle chainring, making shifting onto or off of that one troublesome. I didn't believe it and changed it to 50-40-30 and sure enough it wouldn't shift. I think this is why SRAM hates triples, and now they even hate doubles.
Brian
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Post by wheelson on Apr 10, 2021 13:27:12 GMT
The freewheel will be on it's way Monday. I'm pretty well stocked on Lambert and Viscount stuff. Would you consider letting go of one of those French threaded freewheels? As far as the half-step, it was all related to the shifting pattern with the right and left downtube shifters. With triples, it doesn't break my heart to see them go, one of the big pains at work. The latest Cannondale mountain bikes seem to be doubles and 27.5 (650b) wheels. All the plus and fat bikes are single in the front with huge (40-50ish) low gear cassettes. That shifting can be a bit tricky as well, as in 10 gears and extreme chain lines. Best, John "wheelson"
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Post by brianbutler on Apr 10, 2021 14:00:28 GMT
Yes, I will send you a 14-32T French threaded Suntour Perfect 5-Speed today. Should we just cancel out the shipping charges?
Brian
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Post by wheelson on Apr 10, 2021 14:04:51 GMT
Thanks Brian, works for me. I only have one French bike in my herd, a '60s Motobecane Cyclotouriste. It's currently a 4 speed but I want to squeeze in a 5 and run a single front so I can use the nifty Moto chainguard. Best, John "w"
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Post by brianbutler on Apr 10, 2021 14:47:36 GMT
Thanks Brian, works for me. I only have one French bike in my herd, a '60s Motobecane Cyclotouriste. It's currently a 4 speed but I want to squeeze in a 5 and run a single front so I can use the nifty Moto chainguard. Best, John "w" The freewheel is on its way. It is 70F/21C here and I'm heading out on the first shorts/jersey ride since September.
Brian
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